Pipe plug



Aug. 19, 1952 ANDERSON 2,607,370

PIPE PLUG Filed July 15. 1948 Fla! INVENTOR. 01:42 E mam joints are formed.

Patented Aug. 1 9 1952 UNITED STATE s PATENT 5 *fjfi I PIPE P UGU-QL 1.1]; f j Oscar F. Anderson, Watsonville, v 7 Application July 13, 1918, Serial No.38,$71 g f This invention relates to devices for .sealing the ends of pipes, and particularly to plugs designed as pres-sure test heads adapted for use in testing piping or tubing under pressure.

In many branches of industry wherein piping is used under pressure it is customary to use plain-end pipe, suitable for use 'With welded joints, and without threads or flanges.

such pipe or tubing is used under pressure it is Where necessary that it be tested to insure that no leakage occurs, and in most cases it is necessary that these tests be made section by section as the pipe mus-t be sealed againstv the test pressure, and the usual practice in such cases is to clamp a test head or'cap to the open. end of the length of pipe under test. The most usual clamping means employed comprises two half "sections which are bolted around the abutting joint between the pipe and the test head with a sealing gasket compressed against the joint by the clamp and gripping means vorrdogs engaging both the pipe and the test head surfaces. The application of such a clamping means is asomewhat laborious process, as is its subsequent removal. This -involves the time of' skilled workers and is an expensive operation.

To avoid the difficulties thus involved numercus "types of plugs and caps have been devised, but all of them have had disadvantages, some of these serious. Modern practice involves the use of higher and higher pressures, and with all of the devices with which I am familiar any inadvertent loosening of the plug (which insome cases I is quite likely to occur) may be-followedbythe device being blown out of the pipe, sometimes with great force, and always :with the possibility of destruction of property if not ofllife,

, 'The broad objec'toit-his invention is to provide a light portable test plug which would be free from these disadvantages and dangers, whether employed as a test head, or for any other purpose for which a temporary seal against pressure may i be necessary. Pursuant to this broad purpose, among the-objects of my invention are to provide' a plug which is applicable to any type of V pipe,fwhether plain end, threaded, or flanged; to provide a pressure plug which may be applied or released'in'a matter ofseconds; and, most important, to provide .a locking and sealing device wherein the pressure within'the pipe itself is effective to tighten and retainthe seal, so that inadvertent slipping, leakage, or ejection is impossible.

Considered broadly, the pipe plug of my in- 'In such cases the end of the a Qlaims. '(ol. 138 -89) ven tion comprisesa central,stem,.usuallytubular,

onwhich are carried means" for supportingit coaxially, within the pipe. Also mounted .on the stem, is an annular cup, ,preferab1y-. cf synthetic rubber, but whichmay also,be ofnaturalrubber or. other, resilient material. {.The cylindrical skirts of this cup are; directed .inwardlyzof; the pipe to be, tested, and' -are adapted tobear, respectively, against the inner stem and the inner wall' of the pipe itself the interior'ofrthefcup being open to the pressure within thepipe. Means are provided, for, applyingnmechanical pressure longitudinally of the cup; which'bulges the outer wall in'toactualcontact with; the pipe.

'itself,.and the inner skirt into contact with .the stem. As a result; of this;. ;-construction, :when

fluid pressure, is appliedwithin the pipe it, tends ,to

.force the skirts against the surfaces vwith which they abut, and the greater the press-urewithin the pipethe greaterthe force applied. againstthe skirts to hold them, into contact :Withthese-surfacesgand to ,preyent leakage; As a result, even when the compression originally placedja'gainst the cup is released, I have found that thefluid pressure within thepipe will hold the device in place, and that it cannot be removedjrornthe pipe until the internal; pressure hasjbeen reduced.

' Theinvention,maybe moreclearlyappreciamdL and the other objects and advantages inherent inits design and usebe un derstood,-.by reference ent: in,

Y showing the device when sealedintq-thepipe;

,. Fi ,3 isia. vie o itudinallroi the science showing the stem inflsectionandqthe lejyer mountring in elevation I Figi 4 is an end view v of, thejgjd mechanism which engages the-pipe wall :andi-serves also, for centering the stem withinthe pipe; and holding it in position thereprior to the'eXpansionjof-the sealj'an'd i Fig. .5" isianelevationalview, partly. in section,

' showing an alternative form of resilient-"cup;

. Thepreferred form of .theidevice'shown inrthe figurescompri ses .a central niounting stemiil,

which is preferably made tubular :and provided with external threads at its inner end on which are threaded a flange 2 of somewhat smaller diameter than the pipe to be tested, and internal threads at its outer end for engaging the connections 3 to the pressure gauge and compressor (not shown). Where the device is to be used as a plug only, and not as a test head, the stem may be made solid, or a plug may be threaded into the stem for this purpose if it is hollow. A cam lever A is pivotally mounted upon the stem on trunnions 5. The cam end of the lever fits against aflangedkor skirted annulus sliding it along the: stem I away from the trunnions when the lever is folded into the position of Fig. 2.

The depending skirt of the flange 6 bears against dogs 1 which slide in grooves formed in" a frusto-conical member 8 also slidably mounted on the stem, these dogs being retained in p.osi-. tion by a spring ring 9.

Movement of the ele ment 6 by the lever forces, the dogsl'toward the 7 base of the cone and hence outwardly into contact with the walls of ,the pipe ll. Whenthey have contacted these walls, their outward move- .xcnient being re'sisted,'they'a1so force the member t1 along the stem I until its motion also is re- 'rsisted. Owing to the mechanical advantage of the longitudinal resistance which is inherent in :th'e-long taper of the member' il, ome outward motion of thedogs'l continues, until the device is firmlylocked in the pipe.

:iThelongitudinal resistance is oifered by the either case the cup has a dependentinner skirt I2, preferably-but not necessarily, feather-edged as shown, and a longer thicker outer skirtlS 4 and the fact that the vents I5, It, or both, admit the full pressure within the pipe into the interior of the cup. Should there be any tendency to leakage, either around the stem or against the inner wall of the pipe, the pressure external to the cup I0 is less than that within it, and as a result the skirts of the cup are forced against the elements with which they abut, closing the leak and improving the seal. The pressure within the cup likewise exerts a longitudinal force against frustoconical member 8 Whichterids to morefirmly hold dogs I in engagement with the pipe. This 'action' is so powerful that once the seal has been formed against internal pressure, lever 4 may be releasedwithout the device blowing out of the pipe.

,On the other hand, when the pressure within the pipe is removed, the device immediately releases, and in case the dogs I still hold against the pipe II a slight tap with a hammer, or rotation 'lof the stem, will immediately release them. v

To'facilitate engaging connections :3 to pressure gauge and compressor, two sides of the'stem may be flattened, as indicated by the reference characters 28, to receive a Wrench.

NVhile I'presentlyprefer-the form of the device shown in the drawings and here described, be-

causeofits simplicity and ruggedness'it is ob- 'which'b'ears against the flange 2. It is important 'that the'latter be'provided with on'e'ormore vents '|5,:-th'at a vent 16 to the interior'of the oup .be provided in .the stem I',orboth, sothat *the interior of the cup may be open to the pressure within the pipe. i

Prior to'inserting thedevice into the pipe for {:test, fl'ange Z I may be adjusted on its threads so filial? whenthe lever-isimoved into position-as snown T inFig; 2 the compression exerted longitudinally of the cup will force the outer skirt into firmcontact with the wall of the pipe. A reasonable variation in pipe diameter can be taken care'of in this fashion. Preferably a cotterpin I8 or other means for retainingb flange 2 .against accidental loss when the deviceis not in :use'isalso provided. a a L;

is shownin Fig. 2, the operation of lever 4 compresses; the cup, flattens the 'bottom surface thereof, and forcesthe skirts l 2- and I 3 'into'firm contact with the's tem and thepipe respectively andatthe same time causes the dogs"! to engage "pipe (I. Materials ofthe class used for this cup are almost incompressible, volumetric'ally', and

" the-eonin'g of the bottom of the cupin either di- -"-rection tends to improve thejseal 'fornied," although .the' device is operative when the bottom of the I in the pipe, 'andmeans'for compressing said cup longitudinally to force said skirts into contact.

2. A pipe plug in accordance with claim 1 I wherein said cup is provided with a bottomof frusto-conical form against which said compressingmeans bears. I

" 3. A pipe plug in accordance with claim 1 wherein said 'compressingmeans comprises an annular flange mounted on said stem .and bearing against one of said skirts internallyi'of the REFERENCES "CITED 7 The following referencesare of rcordin the si for this patent:

v UNITED STATES ATENTS".

:Nnmber 'Name i :Date, 739,589 Clifford; Sept.' 22, 1903 "910,966 Simon Jan. 26,1909 1 922,544 Turner et a1. May 25,1909 ,11',6l6,39 2 Provost Feb. ;1, .1927 1,788,845 Reynolds l ..Jan. 13,1931 Nicholson vMay-l, 1945 

